As a resin composition for encapsulation to be used at encapsulation of optical semiconductor elements such as light-emitting diodes (LED), it is required for a cured material of the composition to have transparency. In general, epoxy resin compositions obtained using epoxy resins such as bisphenol A epoxy resins or alicyclic epoxy resins and acid anhydrides as curing agents have been widely used.
In the case where the epoxy resin compositions are used as encapsulating materials of optical semiconductor elements, a sufficient light resistance has not been obtained in optical semiconductor devices obtained from the encapsulation, with the shortening of an emission wavelength (e.g., 350 to 500 nm).
For the reasons, in order to achieve an improvement in the light resistance, an epoxy resin composition for optical semiconductor element encapsulation using a specific silicone resin has been proposed (see Patent Document 1).
Patent Document 1: JP-A-2006-274249